Page:In the high heavens.djvu/382

378 Critical velocities on the sun and planets, 314 Cygnus, new star in, 215-216 61 Cygni, distance of, 13

, the point to which the solar system is moving, 25 Dunér's measurement of the rotation of the sun, 166

, the, its interior heat, 34 its past history, 34, 36 its ancient heat-stages, 36 gaseous and nebular stage, 37 and man, 39 an average specimen of a world, 39 its movement on its axis, 64 is the earth rigid? 75, 76 distances from the sun, 116 ""Mars, 117 absence of free hydrogen, why, 128-131 the fate of oxygen, 137 and the Nebular Hypothesis, 228 the destiny of species, 253-256 coal supply, 257 stores of energy, 258 sources of heat, 261-263 viewed from Alpha Centauri, 330 equilibrium of our atmosphere, 372 (See also Volcanoes.) Eclipse, the, of 1893— conditions essential to observation, 77 duration of totality, 78 the journey of the moon's shadow, 79-83 speed of the journey, effect of curvature of the globe, 82, 83 the best sites for observation, 83-84 present-day problems for solution, 85-88 Eclipse, preliminary inquiries, 88-91 Epsilon Lyræ, 201 Euclid and the problem of space, 249-251 Eyes of extinct animals, 17

, Mr., and the eclipse of 1893, 92

, distinctive velocity of molecules, 127 character of molecules, 356-360 dimensions of molecules, 361 velocity of molecular movements, 360, 361 pressure of gases, 362-364 effect of heat, 365, 369 vibration of molecules, 366, 367 experiments with hydrogen, 368 heat and light due to vibration, 369 iron-gas spectrum, 368 the molecular theory and solar physics, 369 Helmholtz's solar researches, 369-370 free hydrogen absent from our atmosphere, 128-131 hydrogen in Sinus and Vega, 131 knowledge of spectrum of hydrogen due to Sirius, 165 hydrogen in Mars, 133 Dr. Stoney's gaseous theory, 128 oxygen on Mars, 133 velocity of aqueous vapour molecules, 133 Dr. Huggins' discoveries, 157 Geology, the uniformitarian hypothesis controverted, 336 Gill, Sir David, and the photographic chart of the heavens, 167 Gravitation, the law of, 196 is it universal? 188, 197 planets and the law, 198 the law in our system, 199